Blood gas exchanger with restriction element or elements to reduce gas exchange

ABSTRACT

Described is a gas exchanger with a restriction element or elements to reduce gas exchange as desired to avoid hypo-capnia and hyper-oxygenation in small patients. The gas exchanger includes a gas exchanger housing with an outer wall and a core which defines an inner wall and having a blood inlet for receiving a blood supply and a blood outlet. The gas exchanger also includes: a hollow fiber bundle disposed within the housing between the core and the outer wall; and a gas inlet compartment for receiving an oxygen supply and directing the oxygen supply to first ends of the hollow fiber bundle, wherein the gas inlet compartment includes at least one restriction element configured to allow the oxygen supply to reach only a portion of the hollow fiber bundle.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/571,548, filed Nov. 3, 2017, which is a national stage application ofPCT/IB62015/053493, filed May 12, 2015, which is herein incorporated byreference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to extracorporeal fluidcircuits. More specifically, the disclosure relates to an oxygenator, orgas exchanger, used in such circuits having at least one restrictionelement that allows for a reduction in gas exchange to avoid hypo-capniaand hyper-oxygenation in small patients.

BACKGROUND

The disclosure pertains generally to blood processing units used inblood perfusion systems. Blood perfusion entails encouraging bloodthrough the vessels of the body. For such purposes, blood perfusionsystems typically entail the use of one or more pumps in anextracorporeal circuit that is interconnected with the vascular systemof a patient. Cardiopulmonary bypass surgery typically requires aperfusion system that provides for the temporary cessation of the heartto create a still operating field by replacing the function of the heartand lungs. Such isolation allows for the surgical correction of vascularstenosis, valvular disorders, and congenital heart defects. In perfusionsystems used for cardiopulmonary bypass surgery, an extracorporeal bloodcircuit is established that includes at least one pump and anoxygenation device to replace the functions of the heart and lungs.

More specifically, in cardiopulmonary bypass procedures oxygen-poorblood, i.e., venous blood, is gravity-drained or vacuum suctioned from alarge vein entering the heart or other veins in the body (e.g., femoral)and is transferred through a venous line in the extracorporeal circuit.The venous blood is pumped to an oxygenator that provides for oxygentransfer to the blood. Oxygen may be introduced into the blood bytransfer across a membrane or, less frequently, by bubbling oxygenthrough the blood. Concurrently, carbon dioxide is removed across themembrane. The oxygenated blood is filtered and then returned through anarterial line to the aorta, femoral artery, or other artery.

In small patients, particularly neonatal patients, with low bloodvolumes, if a standard sized oxygenator is used during cardiopulmonarybypass, excessive carbon dioxide removal and excessive oxygen deliverycan result. Excessive carbon dioxide removal can lead to a deleteriouschange of pH of the blood out of the physiological levels. Avoidingexcessive carbon dioxide removal and excessive oxygen delivery is,therefore, desired.

SUMMARY

Example 1 of the present disclosure is a gas exchanger comprising: a gasexchanger housing including an outer wall and a core which defines aninner wall and having a blood inlet for receiving a blood supply and ablood outlet, the gas exchanger housing defining a gas exchanger volume;a hollow fiber bundle disposed within the housing between the core andthe outer wall, the hollow fiber bundle comprising hollow gas permeablefibers, each fiber having first and second ends and a hollow interior;and a gas inlet compartment for receiving an oxygen supply and directingthe oxygen supply to the first ends of the hollow gas permeable fibers;wherein the gas inlet compartment includes at least one restrictionelement configured to allow the oxygen supply to reach only a portion ofthe hollow gas permeable fibers.

Example 2 is the gas exchanger of Example 1, wherein the at least onerestriction element comprises a gasket.

Example 3 is the gas exchanger of Example 1, wherein the at least onerestriction element is moveable such that the at least one restrictionelement can assume a first position that is opened in order to allow theoxygen supply to reach all of the hollow gas permeable fibers and asecond position that is closed such that the oxygen supply only reachesa portion of the hollow gas permeable fibers.

Example 4 is the gas exchanger of Example 1, wherein the gas exchangerincludes at least two restriction elements and the at least tworestriction elements are concentrically arranged.

Example 5 is the gas exchanger of Example 1, wherein the gas exchangerhousing is tubular in shape, the gas inlet compartment includes a gasinlet that is located at or near the center of the lid, and the at leastone restriction element concentrically surrounds the gas inlet.

Example 6 is the gas exchanger of Example 1, wherein 50% of the fiberbundle is provided with oxygen supply for a small, neonatal patient.

Example 7 is a gas exchanger comprising: a gas exchanger housingincluding an outer wall, at least one lid, and a core which defines aninner wall and having a blood inlet for receiving a blood supply and ablood outlet, the gas exchanger housing defining a gas exchanger volume;a hollow fiber bundle disposed within the housing between the core andthe outer wall, the hollow fiber bundle comprising hollow gas permeablefibers, each fiber having first and second ends and a hollow interior,wherein the first ends of the hollow gas permeable fibers are located ina first potting that is located at or near the lid; and a gas inletcompartment including a gas inlet for receiving an oxygen supply anddirecting the oxygen supply to the first ends of the hollow gaspermeable fibers; wherein the gas inlet compartment includes at leastone restriction element that concentrically surrounds the gas inlet,wherein the one or more restriction elements are moveable such that theone or more restriction elements can assume a first position that isopen in order to allow the oxygen supply to reach all of the first endsof the hollow gas permeable fibers and a second position that iscompressed against the potting such that the oxygen supply only reachesa portion of the hollow gas permeable fibers.

Example 8 is the gas exchanger of Example 7, further comprising at leastone rigid lever that is connected to the at least one restrictionelement and that is configured to move the at least one restrictionelement between the first and second positions.

Example 9 is the gas exchanger of Example 7, wherein the gas inletcompartment is located within the at least one lid.

Example 10 is the gas exchanger of Example 7, wherein the oxygenatorincludes at least two restriction elements and the at least tworestriction elements are concentrically arranged.

Example 11 is the gas exchanger of Example 7 wherein the at least onerestriction element comprises a gasket.

Example 12 is the gas exchanger of Example 7, wherein 50% of the fiberbundle is provided with oxygen supply for a small, neonatal patient.

Example 13 is a method of oxygenation comprising: providing a gasexchanger comprising: a gas exchanger housing including an outer walland a core which defines an inner wall and having a blood inlet forreceiving a blood supply and a blood outlet, the gas exchanger housingdefining a gas exchanger volume; a gas inlet compartment for receivingan oxygen supply and directing the oxygen supply to the first ends ofthe hollow gas permeable fibers; wherein the gas inlet compartmentincludes at least one restriction element configured to allow the oxygensupply to reach only a portion of the hollow gas permeable fibers;activating the at least one restriction element; causing the oxygensupply to flow through the hollow interior of the portion of the hollowgas permeable fibers; delivering blood to the gas exchanger through theblood inlet; causing the blood to flow through the gas exchanger housingover the exterior of the hollow gas permeable fibers; and dischargingthe blood through the blood outlet.

Example 14 is the method of Example 13, wherein the at least onerestriction element comprises a gasket.

Example 15 is the method of Example 13, wherein the at least onerestriction element is moveable such that the at least one restrictionelement can assume a first position that is open in order to allow theoxygen supply to reach all of the hollow gas permeable fibers and asecond position that is closed such that the oxygen supply only reachesa portion of the hollow gas permeable fibers.

Example 16 is the method of Example 15, wherein activating the at leastone restriction element comprises moving the at least one restrictionelement to the second position.

Example 17 is the method of Example 13, wherein the gas exchangerincludes at least two restriction elements and the at least tworestriction elements are concentrically arranged.

Example 18 is the method of Example 13, wherein the gas exchangerhousing is tubular in shape, the gas inlet compartment includes a gasinlet that is located at or near the center of the lid, and the at leastone restriction element concentrically surrounds the gas inlet.

Example 19 is the method of Example 13, wherein the at least onerestriction element concentrically surrounds the gas inlet, wherein theone or more restriction elements are moveable such that the one or morerestriction elements can assume a first position that is open in orderto allow the oxygen supply to reach all of the first ends of the hollowgas permeable fibers and a second position that is compressed againstthe potting such that the oxygen supply only reaches a portion of thehollow gas permeable fibers.

Example 20 is the method of Example 13, wherein 50% of the fiber bundleis provided with oxygen supply for a small, neonatal patient.

While multiple embodiments are disclosed, still other embodiments of thepresent disclosure will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the disclosure. Accordingly, the drawingsand detailed description are to be regarded as illustrative in natureand not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an oxygenator, or gas exchanger, inaccordance with embodiments of the disclosure.

FIG. 2 is a cross-sectional view of the oxygenator of FIG. 1 taken at2-2.

FIG. 3 is a partial cross-sectional view of an oxygenator in accordancewith embodiments of the disclosure.

FIG. 4 is a partial cross-sectional view of an oxygenator in accordancewith embodiments of the disclosure.

FIG. 5 is a partial cross-sectional view of an oxygenator in accordancewith embodiments of the disclosure.

FIG. 6 is a schematic cross-sectional view of an oxygenator inaccordance with embodiments of the disclosure.

FIG. 7 is a cross-sectional view of an embodiment of an oxygenator inaccordance with embodiments of the disclosure.

FIG. 8A is a partial cross-sectional view of an oxygenator in accordancewith embodiments of the disclosure.

FIG. 8B is a cross-sectional view of the oxygenator of FIG. 8A taken atB-B.

While the disclosure is amenable to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and are described in detail below. Theintention, however, is not to limit the disclosure to the particularembodiments described. On the contrary, the disclosure is intended tocover all modifications, equivalents, and alternatives falling withinthe scope of the disclosure.

DETAILED DESCRIPTION

The disclosure pertains to an oxygenator (also commonly referred to as agas exchanger). In some embodiments, an oxygenator may be used in anextracorporeal blood circuit. An extracorporeal blood circuit, such asmay be used in a bypass procedure, may include several differentelements such as a heart-lung machine, a blood reservoir, a heatexchanger, as well as an oxygenator. In various embodiments, the gasexchanger, or oxygenator, includes one or more restriction elements thatallow for a reduction in gas transfer performance of the oxygenator inorder to avoid hypo-capnia and hyper-oxygenation in patients,particularly small or neonatal patients. In various embodiments, one ormore restriction elements are configured to be activated to allow anoxygen supply to reach only a portion of hollow gas permeable fibers,thereby reducing the amount of gas exchange performed by the oxygenator.

FIG. 1 is a schematic illustration of an oxygenator 10 (or “gasexchanger”). While the internal components are not visible in theillustration, the oxygenator 10 will include a fiber bundle inside wheregas exchange takes place. The oxygenator 10 includes a housing 12, afirst end cap 14 that is secured to the housing 12 and a second end cap16 that is secured to the housing 12. In some embodiments, the housing12 may include other structures that enable attachment of the housing 12to other devices. While the housing 12 is largely cylindrical in shape,in some embodiments, the housing 12 may have a triangular, rectangularor other parallelogram cross-sectional shape, for example. The fiberbundle inside may have generally the same sectional shape as the housing12 or may have a different sectional shape.

In some embodiments, a blood inlet 18 extends into the housing 12 and ablood outlet 20 exits the housing 12. As noted, the oxygenator 10includes a fiber bundle inside where gas exchange takes place, and thusincludes a gas inlet 22 and a gas outlet 24. In some embodiments, theoxygenator 10 may include one or more purge ports 30 that may be usedfor purging air bubbles from the interior of the oxygenator 10.

The positions of the blood and gas inlets and outlets, and the purgeport 30 in FIG. 1 are merely illustrative, as other arrangements andconfigurations are also contemplated. The purge port 30 may include avalve or a threaded cap. The purge port 30 operates to permit gases(e.g., air bubbles) that exit the blood to be vented or aspirated andremoved from the oxygenator 10.

The housing 12 is preferably made of a rigid plastic in order for theoxygenator 10 to be sturdy yet lightweight. The oxygenator is alsopreferably mainly transparent, in order to allow the user to see throughthe oxygenator. Therefore, a preferred material for the oxygenator is atransparent, amorphous polymer. One exemplary type of such a material isa polycarbonate, an ABS (Acrylonitrile Butadiene Styrene), or aco-polyester. Other suitable materials for the housing are alsocontemplated.

The fiber bundle (not shown in FIG. 1) inside housing 12 may include anumber or plurality of microporous hollow fibers through which a gassuch as oxygen may flow. The blood may flow around and past the hollowfibers. Due to concentration gradients, oxygen may diffuse through themicroporous, semi-permeable hollow fibers into the blood while carbondioxide may diffuse into the hollow fibers and out of the blood.

In some embodiments, the hollow fibers are made of semi-permeablemembrane including micropores. Preferably, the fibers comprisepolypropylene, polyester, or any other suitable polymer or plasticmaterial. According to various embodiments, the hollow fibers may havean outer diameter of about 0.25 to about 0.3 millimeters. According toother embodiments, the microporous hollow fibers may have a diameter ofbetween about 0.2 and 1.0 millimeters, or more specifically, betweenabout 0.25 and 0.5 millimeters. The hollow fibers may be woven into matsthat can range from about 50 to about 200 millimeters in width. In someembodiments, the mats are in a criss-cross configuration. The fiberbundle may be formed of hollow fibers in a variety of winding patternsor structures.

The hollow fibers are embedded, or sealed, at their ends, in rings ofpolyurethane resin, for example, which is known as “potting.” The fiberbundle of hollow fibers is preferably in a cylindrical shape, but othershapes are also contemplated. The hollow fibers, at first ends, areconnected to the first end cap 14 through the potting, with the gasinlet 22 being located in the first end cap 14. At second ends, thehollow fibers are connected to the second end cap 16 through the pottingwith the gas outlet 24 being located in the second end cap 16. Theinternal lumens of the fibers are part of the gas pathway that isdetermined by the fist end cap 14, the potting at the first end, thefibers, the second potting and the second end cap 16. The oxygenatorchamber is thus defined by the housing as an outer wall and an innerwall or core, together with the pottings at each end of the hollowfibers.

Oxygen, or a mixture of oxygen and air, known as an oxygen supply,enters through gas inlet 22, passes through the microporous hollowfibers within the fiber bundle, and exits the oxygenator 10 through thegas outlet 24. In some embodiments, the pressure or flow rate of oxygenthrough the oxygenator may be varied in order to achieve a desireddiffusion rate of, for example, carbon dioxide diffusing out of theblood and oxygen diffusing into the blood. In some embodiments, asillustrated, the oxygen flows through the hollow fibers while the bloodflows around and over the hollow fibers.

Differences in concentration of gases between the blood and the oxygensupply produce a diffusive flow of oxygen toward the blood and of carbondioxide from the blood in the opposite direction. The carbon dioxidereaches the gas outlet 24 and is discharged from the oxygenator 10.

Any suitable gas supply (or oxygen supply) system may be used with theoxygenator 10 of the disclosure, in order to deliver an oxygen supply tothe fiber bundle or hollow fibers of oxygenator 10. Such a gas supplysystem may also include, for example, flow regulators, flow meters, agas blender, an oxygen analyzer, a gas filter, and a moisture trap.Other alternative or additional components in the gas supply system arealso contemplated.

As shown in FIG. 1, in some embodiments, structural features may beincluded within oxygenator 10, and specifically within the first end cap14 in the figure, that allow an oxygen supply delivered to theoxygenator 10 to reach only a portion of the hollow fibers in the fiberbundle where gas exchange takes place. The restriction elements areconfigured to be either in an open/inactivated position or aclosed/activated position. Moving the at least one restriction elementto a closed or activated position will result in an oxygen supply beingdelivered to only a portion of the hollow fibers in the fiber bundle,and thereby will reduce gas transfer performance. The disclosureprovides a way to decrease gas exchange efficiency of the oxygenator 10in order to avoid excessive carbon dioxide removal and excessive oxygendelivery to small patients, including neonatal patients.

FIG. 1 shows two restriction elements, first restriction element 32 andsecond restriction element 34, extending from or within first end cap14. Although two restriction elements are shown, it is contemplated thatany number of restriction elements may be included, such that the sizeof the first end cap 14 may accommodate the restriction elements. Thefigure also shows two levers or arms 36 and 38 that extend from or thatare coupled or attached to the restriction elements 32, which are usedto move the restriction elements between a restricted or closedconfiguration and an unrestricted or open configuration. Levers or arms36, 38 are exemplary structural features used to move the restrictionelements 32, 34, but other suitable features are also contemplated bythe disclosure.

FIG. 2 is a cross-sectional view of the first end cap 14 shown in theembodiments of the disclosure in FIG. 1 taken at line 2-2. FIG. 2 showsthat restriction elements 32 and 34 are circular in shape and areconcentrically arranged and surrounding gas inlet 22. The circular shapeis one exemplary cross-sectional shape of the restriction elements 32and 34, but other shapes are also contemplated by the disclosure. Therestriction elements 32, 34 may be gaskets, for example, although otheroptions are also contemplated. Preferably, such gaskets may be made froma silicone or any soft rubber-like material that is able to provide anairtight seal with the polymeric wall of the end cap 14. The silicone orrubber-like material of the restriction elements may also be supportedby a rigid material in order to provide rigidity to the gasket and allowit to open and close.

FIGS. 3, 4 and 5 are partial cross-sectional perspective views ofoxygenator 10. FIG. 3 shows the oxygenator 10 with both restrictionelements 32, 34, in an open or inactivated configuration. FIG. 4 showsthe same view as in FIG. 3, but with restriction element 32 being in aclosed or activated configuration. FIG. 5 shows the same view again asin FIGS. 3 and 4, but with restriction element 34 being in a closed oractivated configuration.

FIGS. 3, 4 and 5 show cross-sectional views of circular-shaped,restriction elements 32, 34, with rigid levers 36, 38 attached,respectively. The levers 36, 38 that are attached to or an extension ofrestriction elements 32, 34 are one example of a feature that may beused to move the restriction elements between an inactivatedconfiguration and an activated configuration or vice versa. Othermethods or structural features that would allow the restriction elementsto be moveable between the two configurations are also contemplated bythe disclosure. For example, a pre-loaded spring (not shown) may beprovided in order to move the restriction elements between an open and aclosed position. Alternatively, a snap (not shown) may be used to fixthe restriction elements in an open or a closed position. Anotheralternative restriction element is shown in FIGS. 8A and 8B, and isdescribed in detail below.

Fiber bundle 40, made up of a plurality of hollow fibers (not shownindividually), is shown with a potting 42 on first ends of the hollowfibers. A gas inlet compartment 44 is formed within first end cap 14between the gas inlet 22 and potting 42. The gas-holding capacity orsize of the gas inlet compartment 44 is determined by whether therestriction elements 32, 34 are activated or not.

FIG. 4 shows restriction element 32 in the closed or activatedconfiguration. In order to activate the restriction elements 32, 34, thelevers 36, 38 may be pushed, which moves the restriction elements 32, 34inward through the gas inlet compartment 44 and towards potting 42. Oncethe restriction elements 32, 34 are in contact with potting 42, theportion of the gas inlet compartment 44 that is capable of filling withthe gas or oxygen supply is reduced. Also, the portion of the hollowfibers in fiber bundle 40 that are able to be reached by the oxygensupply is reduced. Oxygen supply coming in through gas inlet 22 is onlyable to reach the portion of the hollow fibers in fiber bundle 40 withfirst end openings that are located between gas inlet 22 and theactivated restriction element 32 or 34. FIG. 5 shows restriction element34 in an activated configuration. Compared to FIG. 4, where restrictionelement 32 is activated, a greater number of hollow fibers would be ableto receive oxygen supply in the fiber bundle in FIG. 5; however it wouldstill only be only a portion of the hollow fibers in the whole fiberbundle 40. Any number and locations of restriction elements may beincluded in embodiments of the disclosure, as can be accommodated by thesize of the oxygenator 10.

FIG. 6 is a schematic view of a portion of a cross-section of theoxygenator 10 shown in FIG. 1. The portion shown includes core 50 of thehousing 12, which is not shown in previous figures. In FIG. 6,restriction element 34 is activated and in contact with potting 42. Onlyhollow fibers making up the fiber bundle 40 that are to the interior ofthe restriction element 34 are active or effective and able to receiveoxygen supply. The dotted lines mark the outer perimeter of the activeor effective fibers, which are bracketed and marked as 60 in the figure.This configuration is possible if a gas inlet connector (not shown) isto the interior of restriction element 34. If, however, the gas inletconnector (not shown) is to the exterior of the restriction element 34,then the hollow fibers of the fiber bundle that are to the exterior ofthe restriction element 34 would be active or effective and able toreceive oxygen supply.

FIG. 7 is a cross-sectional view of another embodiment of an oxygenator100 of the present disclosure. The oxygenator of the present disclosurecan stand alone or, as shown, oxygenator 100 can include an integratedheat exchanger 118. In the particular embodiment shown, blood flowthrough the heat exchanger portion 118 is circumferential, while bloodflow though the gas exchanger portion is longitudinal. Otherarrangements are contemplated, however. As shown in FIG. 7, theoxygenator 100 includes a housing 102, a first end cap 104, and a secondend cap 106. The oxygenator 100 includes a blood inlet 108 and a bloodoutlet 110. A gas inlet 112 permits oxygen to be provided to the gasexchanger portion, while a gas outlet 114 permits gases to exit theoxygenator 100.

The oxygenator 100 includes a heat exchanger core 116, a heat exchangerelement 118 disposed about the heat exchanger core 116, a cylindricalshell 120 disposed about the heat exchanger element 118 and a gasexchanger element 122, all disposed inside the outer shell or housing102. The heat exchanger element 118 and the gas exchanger element 122may each include a number of hollow fibers as discussed with respect tooxygenator 10 (FIGS. 1-6). In some embodiments, the housing 102 includesan annular portion 124 that is in fluid communication with the bloodoutlet 110.

In use, blood enters the blood processing apparatus or oxygenator 100through the blood inlet 108 and passes into the heat exchanger core 116.The blood fills the heat exchanger core 116 and exits through anelongate core aperture 126 and thus enters the heat exchanger element118. In some embodiments, the heat exchanger core 116 includes a singleelongate core aperture 126, while in other embodiments, the heatexchanger core 116 may include two or more elongate core apertures 126.In some embodiments, the elongate aperture 126 allows or directs bloodto flow through the heat exchanger element 118 in a circumferentialdirection.

As shown in FIG. 7, according to some embodiments, the cylindrical shell120 includes an elongate collector or channel 127. The channel 127 maybe disposed at a location substantially diametrically opposed to thelocation of the elongate core aperture 126. Locating the channel 127substantially opposite the location of the core aperture 126 causesblood to flow in a generally circumferential flow pattern within theheat exchanger element 118. The channel 127 may extend from betweenabout 1 and about 15 degrees about the circumference of the cylindricalshell 120. In one exemplary embodiment, the channel 127 extends about 5degrees about the circumference. The blood flow path can becircumferential, as described. Some other alternatives to the blood flowpath, however, include radial or longitudinal flow or combinations ofcircumferential, radial and/or longitudinal flow.

After blood passes through the heat exchanger element 118, it collectsin the channel 127 and flows into an annular shell aperture 128. Theshell aperture 128, in various embodiments, extends entirely orsubstantially around the circumference of the cylindrical shell 120,such that blood exits the inner cylindrical shell 120 around the entireor substantially the entire circumference of the cylindrical shell 120.In some embodiments, the radially disposed shell aperture 128 may belocated near an end of the oxygenator 100 that is opposite the bloodoutlet 110, thereby causing the blood to flow through the heat exchangerelement 118 in a longitudinal direction. Blood then collects in theannular portion 124 before exiting the oxygenator 100 through the bloodoutlet 110.

At least one restriction element 132, as in the embodiment shown in FIG.7, would be located radially outward from, and circumferentiallysurround, the gas inlet 112. Restriction element 132 would include alever or another activation member 136 that would allow the restrictionelement 132 to be moved to contact the potting of the fiber bundle inorder to reduce the number of hollow fibers in the fiber bundle of thegas exchanger element 122 that receive oxygen supply.

The embodiment shown in FIG. 7 is one exemplary integrated oxygenatorand heat exchanger. The oxygenator of the present disclosure may or maynot include a heat exchanger component. Also, other embodiments ofintegrated oxygenators and heat exchangers are contemplated by thedisclosure that may include other configurations and blood flowpatterns. The embodiment shown in FIG. 7 is one example.

FIGS. 8A and 8B show two different cross-sections of another embodimentof the gas exchanger, or oxygenator, of the present disclosure. FIG. 8Ais a partial cross-section of the gas exchanger 200 takenlongitudinally, and FIG. 8B is a cross-section taken at line B-B fromFIG. 8A. The oxygenator 200 has a housing 212 surrounding a plurality ofhollow fibers 240 (not shown individually). A potting is shown by 210.One end cap 214 is shown that includes a gas inlet 222. A generallycircular-shaped restriction element 250 is included in the end cap 214.The restriction element 250 is able to be rotated in two directions asshown by the arrow on FIG. 8B. Restriction element 250 includes aplurality of holes 243 or passages that may be lined up or not lined upwith holes or passages 233 in stationary element 232 that may be locatedeither radially inward or outward from restriction element 250.Depending on whether or not the whole fiber bundle or only a portion ofthe fiber bundle is desired to be used for a particular patient, theholes 243 and 233 may or may not be lined up. If the holes 243 and 233are lined up then gas will flow through the whole fiber bundle. If theholes 233 and 243 are not lined up, then the gas may only reach thefibers in the portion of the fiber bundle that is located radiallyoutward from the restriction element 250. This is one more exemplaryembodiment of the gas exchanger of the present disclosure.

The present disclosure allows the use of one device for a range of sizesof neonatal patients. The device allows for ease in setting appropriategas exchange performances based on specific patient dimensions, therebyavoiding excess carbon dioxide removal, particularly for very smallpatients (size 5 kg or less, for example). Gas exchange may be set basedon the amount of fiber bundle that is active or used, based on whetheror not a restriction element is activated or not. With no restrictionelements activated, the percentage of the fiber bundle that is active orused is about 100%. If one restriction element is activated, thepercentage of the fiber bundle that is active or used is about 50%,forexample. If there are two restriction elements included in the device,then the percentage of active fiber bundle could be either about 33% orabout 66%, for example, depending on which restriction element isactivated. The percentages of fiber bundle that may be active or usedmay be varied as well as the number and location of the restrictionelement or elements.

Another embodiment of the disclosure is a method of oxygenation oroxygenating blood. The steps may comprise providing an oxygenatorcomprising: an oxygenator housing including an outer wall and a corewhich defines an inner wall and having a blood inlet for receiving ablood supply and a blood outlet, the oxygenator housing defining anoxygenator volume; a hollow fiber bundle disposed within the housingbetween the core and the outer wall, the hollow fiber bundle comprisinghollow gas permeable fibers, each fiber having first and second ends anda hollow interior; a gas inlet compartment for receiving an oxygensupply and directing the oxygen supply to the first ends of the hollowgas permeable fibers; wherein the gas inlet compartment includes atleast one restriction element configured to allow the oxygen supply toreach only a portion of the hollow gas permeable fibers. The oxygenatormay alternatively be any embodiment as described, suggested or shownherein, or any other suitable oxygenator. The method may furthercomprise: activating at least one restriction element; causing an oxygensupply to flow through the hollow interior of the portion of the hollowgas permeable fibers; delivering blood to the oxygenator through theblood inlet; causing the blood to flow through the oxygenation housingover the exterior of the hollow gas permeable fibers; and dischargingthe blood through the blood outlet. Other methods of oxygenation arealso contemplated by the disclosure.

Various modifications and additions can be made to the exemplaryembodiments discussed without departing from the scope of the presentdisclosure. For example, while the embodiments described above refer toparticular features, the scope of this disclosure also includesembodiments having different combinations of features and embodimentsthat do not include all of the described features. Accordingly, thescope of the present disclosure is intended to embrace all suchalternatives, modifications, and variations as fall within the scope ofthe claims, together with all equivalents thereof.

What is claimed is:
 1. A gas exchanger comprising: a gas exchangerhousing including an outer wall and having a blood inlet for receiving ablood supply and a blood outlet, the gas exchanger housing defining agas exchanger volume; a hollow fiber bundle disposed within the housingand comprising hollow gas permeable fibers, each fiber having first andsecond ends and a hollow interior; and a gas inlet compartment forreceiving an oxygen supply and directing the oxygen supply to the firstends of the hollow gas permeable fibers; wherein the gas inletcompartment includes at least one restriction element and a gas inletconfigured to receive the oxygen supply, the at least one restrictionelement surrounding the gas inlet and configured to allow the oxygensupply to reach only a portion of the hollow gas permeable fibers. 2.The gas exchanger of claim 1, wherein the at least one restrictionelement comprises a gasket.
 3. The gas exchanger of claim 1, wherein theat least one restriction element is moveable such that the at least onerestriction element can assume a first position that is opened in orderto allow the oxygen supply to reach all of the hollow gas permeablefibers and a second position that is closed such that the oxygen supplyonly reaches a portion of the hollow gas permeable fibers.
 4. The gasexchanger of claim 1, wherein the gas exchanger includes at least tworestriction elements and the at least two restriction elements areconcentrically arranged.
 5. The gas exchanger of claim 1, wherein thegas exchanger housing is tubular in shape and the gas inlet is locatedat or near the center of the gas inlet compartment.
 6. The gas exchangerof claim 1, wherein 50% of the fiber bundle is provided with oxygensupply for a small, neonatal patient.
 7. A gas exchanger comprising: agas exchanger housing including an outer wall and at least one lid andhaving a blood inlet for receiving a blood supply and a blood outlet,the gas exchanger housing defining a gas exchanger volume; a hollowfiber bundle disposed within the housing, the hollow fiber bundlecomprising hollow gas permeable fibers, each fiber having first andsecond ends and a hollow interior, wherein the first ends of the hollowgas permeable fibers are located in a first potting that is located ator near the at least one lid; and a gas inlet compartment including agas inlet for receiving an oxygen supply and directing the oxygen supplyto the first ends of the hollow gas permeable fibers; wherein the gasinlet compartment includes a first restriction element having firstpassages and a second restriction element having second passages,wherein the first restriction element is movable to a first position toalign the first passages and the second passages to allow the oxygensupply to reach all of the first ends of the hollow gas permeable fibersand movable to a second position to misalign the first passages and thesecond passages such that the oxygen supply only reaches a portion ofthe hollow gas permeable fibers.
 8. The gas exchanger of claim 7,further comprising at least one rigid lever that is connected to thefirst restriction element and configured to move the first restrictionelement between the first and second positions.
 9. The gas exchanger ofclaim 7, wherein the gas inlet compartment is located within the atleast one lid.
 10. The gas exchanger of claim 7, wherein the firstrestriction element and the second restriction element areconcentrically arranged.
 11. The gas exchanger of claim 7, wherein thegas inlet is situated further from a central axis of the gas exchangerthan the first restriction element and the second restriction element.12. The gas exchanger of claim 7, wherein 50% of the fiber bundle isprovided with oxygen supply for a small, neonatal patient.
 13. A methodof oxygenation comprising: providing a gas exchanger comprising: a gasexchanger housing including an outer wall and having a blood inlet forreceiving a blood supply and a blood outlet, the gas exchanger housingdefining a gas exchanger volume; a hollow fiber bundle disposed withinthe housing and comprising hollow gas permeable fibers, each fiberhaving first and second ends, hollow interior and an exterior; and a gasinlet compartment for receiving an oxygen supply and directing theoxygen supply to the first ends of the hollow gas permeable fibers;wherein the gas inlet compartment includes at least one restrictionelement and a gas inlet configured to receive the oxygen supply, the atleast one restriction element surrounding the gas inlet and configuredto allow the oxygen supply to reach only a portion of the hollow gaspermeable fibers; activating the at least one restriction element;causing the oxygen supply to flow through the hollow interior of theportion of the hollow gas permeable fibers; delivering blood to the gasexchanger through the blood inlet; causing the blood to flow through thegas exchanger housing over the exterior of the hollow gas permeablefibers; and discharging the blood through the blood outlet.
 14. Themethod of claim 13, wherein the at least one restriction elementcomprises a gasket.
 15. The method of claim 13, wherein the at least onerestriction element is moveable such that the at least one restrictionelement can assume a first position that is open in order to allow theoxygen supply to reach all of the hollow gas permeable fibers and asecond position that is closed such that the oxygen supply only reachesa portion of the hollow gas permeable fibers.
 16. The method of claim15, wherein activating the at least one restriction element comprisesmoving the at least one restriction element to the second position. 17.The method of claim 13, wherein the gas exchanger includes at least tworestriction elements and the at least two restriction elements areconcentrically arranged.
 18. The method of claim 13, wherein the gasexchanger housing is tubular in shape and the gas inlet is located at ornear the center of the gas inlet compartment.
 19. The method of claim13, wherein the at least one restriction element concentricallysurrounds the gas inlet, wherein the one or more restriction elementsare moveable such that the one or more restriction elements can assume afirst position that is open in order to allow the oxygen supply to reachall of the first ends of the hollow gas permeable fibers and a secondposition that is compressed against the potting such that the oxygensupply only reaches a portion of the hollow gas permeable fibers. 20.The method of claim 13, wherein 50% of the fiber bundle is provided withoxygen supply for a small, neonatal patient.